Remarkable growth has occurred in the electronics industry in recent years and a demand has arisen for resists which can be used lithographically and which have a high resolving power, in view of the increase in the degree of integration of semiconductor devices and the improvement in fine working techniques which have accompanied this growth.
Hence, there has been a shift away from the negative type resists towards the positive type resists which have superior resolving power.
Compositions which contain an alkali soluble resin and a naphthoquinonediazide compound as a photosensitive material are generally used for positive-type photo-resist compositions. For example, "Novolak type phenolic resin/naphthoquinonediazide substituted compounds" have been disclosed in U.S. Pat. Nos. 3,666,473, 4,115,128 and 4,173, 470, and examples of a novolak resin made from cresols and formaldehyde/trihydroxybenzophenone-1, 2- naphtho-quinonediazidesulfonate esters have been described as very typical compositions by L. F. Thompson in "Introduction to Microlithograhy" (ASC publication, No. 219, pages 112-121).
The novolak resins used as binding agents do not swell and can be dissolved in an aqueous alkali solution, and when the image which has been formed is used as an etching mask it is highly resistant to plasma etching in particular and is consequently very useful in this application. Furthermore, the naphthoquinonediazide compounds which are used as photosensitive materials are used as dissolution inhibitors which reduce the alkali solubility of the novolak resins themselves. They function specifically by increasing the alkali solubility of the novolak resin rather than by producing an alkali soluble substance when they are irradiated with light and broken down, and they are especially useful for positive type photoresists because they undergo a major change in properties when irradiated with light.
Many of the positive type photoresists developed and practically used in the past have contained novolak resins and naphthoquinonediazide based photosensitive materials for this reason.
The developers for these naphthoquinonediahide based positive photoresists normally are an aqueous alkali solution, but if an aqueous alkali solution which contains metal ions is used as a developer, such as in the manufacture of semiconductor elements, this can have an adverse effect on the characteristics of the product. Alkalis which do not contain metal ions, such as quaternary amine hydroxides, e.g., tetramethylammonium hydroxide or trimethyl (2-hydroxyethyl) ammonium hydroxide, are used.
However, puddle development systems are generally used for development in the manufacture of integrated circuits and the wetting properties of the developer are important in such a system. Moreover, in recent years, the degree of integration of integrated circuits has also increased and the wetting properties of the developer have become increasingly important as the wafer size has increased.
However, the wetting properties of developers which do not contain surfactants are poor and sometimes the exposed parts of the resist which should be removed by development are not removed satisfactorily and a slight residue (referred to below as a film residue) is left behind. On other occasions the surface layer of the fine resist pattern in the unexposed parts peels away (referred to below as surface layer peeling) and this surface layer becomes attached to the exposed parts so that development failure occurs.
Furthermore, the technique of adding surfactants to developers to improve their wetting properties is well known, and disclosures in this connection have been made , for example, in JP-A-58-57128, JP-A-60-223120 and JP-A-61-167948 and U.S. Pat. No. 4,576,903. (The term "JP-A" used therein means an "unexamined published Japanese patent application".) However, foaming is liable to occur with developers which contain known conventional surfactants and the bubbles sometimes cause development failure. Moreover, in many cases the temperature dependence is considerable when such developers are used and this has an adverse effect on the photographic speed of the resist. Moreover, few of these materials have an adequate effect in preventing the occurrence of film residues and surface layer peeling. Even when they are effective in respect of foaming, film residues and surface peeling, the extent by which the film is thinned in the unexposed part is sometimes large with an adverse effect on dimensional accuracy, or the cross sectional form of the resist may become trapezoidal with a resulting loss of resolution.
One method of improving the anti-foaming properties involves adding a hydrophilic organic solvent to the developer as suggested, for example, in JP-A-49-91177, JP-A-60-158461, JP-A-60-241051 and JP-A-61-232453 and U.S. Pat. No. 4,741,989, but the addition of small amounts has no effect on the anti-foaming properties or the occurrence of film residue and surface layer peeling. When large amounts are added, the extent of film reduction in the unexposed parts may be increased and there are problems with dimensional accuracy.
Moreover, even when the conventional surfactants and organic solvents are used conjointly this is not satisfactory with respect to all factors, including antifoaming properties, the occurrence of film residues and surface layer peeling, and the prevention of film reduction.
Furthermore, the addition of non-ionic surfactants of the type obtained by the polyoxyethylene condensation of trihydric or higher alcohols has been suggested in JP-A-62-175738, but even these are ineffective with respect to anti-foaming properties.